The first chapter starts with a quick exposition dump to hash out the setting, essentially that MC's family adopted this girl as his sister but treats her as a sort of Cinderella, dumping unwanted chores on her as if it's natural and treating her with a general sense of contempt. Then, out of nowhere, MC suddenly realized that he's been acting like kind of an ass this whole time so he decides to make amends with his sister, switching from abusing her to treating her better than most real life siblings treat each other practically over night, because fixing deeply ingrained negative behavior is as easy as flipping a switch, apparently. As it turns out though, the sister actually enjoyed doing all those chores for MC and either didn't notice or didn't care about the disdain, because she is absolutely devoted to and obsessed with MC, and gets scary whenever he tries to put any distance between them. The MC, perpetually aware that he had been a jerk to her before, refuses to interpret her clearly affectionate behavior as affection. Like, he notices it, he sees her showing affection and internally remarks on how her behavior sure looks like affection, but then he just rejects the obvious reality in front of his face because he thinks it's unlikely for someone who has been Cinderella'd for years to hold any goodwill towards their abusers... and that's it. That's the entire story in a nutshell. It's just multiple different versions of "MC tries to distance himself from sister because he thinks sister hates him; sister pushes back with yandere-ism; sister wins, clings to MC while MC is confused" over and over again. The location changes, the specific circumstances change, but that flow of events is constant in EVERY CHAPTER that I was able to force myself to read in hopes that something would change, that there might be some progress or character development of some kind. nothing changed.